JP3515840B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer. 2. Description of the Related Art Generally, in an image forming apparatus such as a copying machine, a facsimile, a printer, etc., a developing device for developing an electrostatic latent image on an image carrier with a two-component developer composed of a toner and a carrier. And a toner supply device for supplying toner to the developing device. The toner replenishing device includes a full replenishment system for replenishing the developing device with toner in the entire longitudinal direction and an end replenishing system for replenishing the developing device with toner from its end. As a method of controlling the toner concentration of the developer in the developing device, a magnetic sensor is used to detect a change in the magnetism of the developer in the developing device to detect the toner concentration of the developer. In general, a toner density control method is used in which the toner density is determined based on the detection result of the magnetic sensor and the toner replenishment of the toner replenishing device is controlled so that the toner density becomes a target value. Japanese Patent Application Laid-Open No. 4-342274 discloses a developing device used in an image forming apparatus, which is provided with a developer supply section for supplying a developer to a photoconductor and communicating with the supply section. And a toner cartridge for replenishing toner to the developer supply unit, and at least one partition wall capable of opening and closing a region on a side where the toner is drawn from the toner cartridge in a communication portion between the developer supply unit and the toner cartridge. Is provided. [0005] Japanese Patent Application Laid-Open No. 5-265324 discloses that a two-component developer composed of a toner and a carrier is carried and conveyed to a developing area by a developer carrier to develop a latent image on the image carrier to visualize the image. A developing device having a separator for separating the developer on the developer carrier and circulating the developer in the developer storage chamber, and a toner supply mechanism for replenishing toner in the developer in the developer storage chamber. An elastic plate is provided at a position opposite to the toner replenishing portion of the toner replenishing mechanism, and the replenished toner from the toner replenishing portion is caused to collide with the elastic plate, and the collided toner is mixed with the developer flowing on the separator. Is described. Japanese Patent Application Laid-Open No. Hei 6-35319 discloses an image bearing member on which a latent image is formed, and developers of different colors for visualizing the latent image formed on the image bearing member. The developer is agitated by a stirring means, and at the time of development, a magnetic brush is formed on the developer carrier and the magnetic brush is brought into contact with the image carrier to form a latent image on the image carrier. Developing, having a plurality of developing devices in which the magnetic brush on the developer carrier is extinguished at the time of non-development, and toner is supplied to the developer from a toner supply unit,
The stirring means is driven by a common drive source for the plurality of developing devices, the toner concentration of each developer in the plurality of developing devices is detected by the toner concentration detecting means, and based on the detected value of the toner concentration detecting means. In the toner replenishment control method for an image forming apparatus for controlling toner replenishment of the toner replenishment unit, the toner density of the developing device whose developing order is the first among the developing devices in which the stirring means is driven by the common driving source is set to When it is determined that the toner density is low based on the detection value of the toner density detecting means, the current toner density detected by the toner density detecting means and the target toner density are determined by the time immediately before the start of development of the developing device at the next image forming opportunity. Calculate the toner replenishment amount such that the toner concentration of the developing device becomes the target toner concentration, and terminate the development of the developing device with the supplied toner amount. Toner supply control method characterized by performing on average, are described while the said stirring means to the developing immediately before the start of the developing apparatus in the next image forming opportunities are driven from. The full replenishment method is very convenient for the toner density control method because the toner is uniformly replenished into the developing device. However, the toner replenishing device actually has an edge replenishing method due to mechanical restrictions and cost of the device. The edge replenishment method has a problem that compared with the full replenishment method, it takes time for the toner supplied from the end of the developing device to uniformly mix with the developer in the developing device. In the above-mentioned toner concentration control method, in the edge supply method, the toner concentration is detected by a magnetic sensor in a state where the toner supplied from the end of the developing device is uniformly mixed with the developer in the developing device. It is essential that the control section controls the toner replenishment of the toner replenishing device so that the toner concentration becomes a target value based on the detection result of the magnetic sensor. It takes time until the toner concentration is reflected on the detected toner concentration (until the toner is uniformly mixed with the developer), which is an obstacle for performing accurate toner concentration control. The present invention solves the above-mentioned problems, and quickly reflects the toner replenished by the toner replenishing device on the toner density detected by the magnetic sensor even in a system in which the toner replenishing device replenishes toner from the end of the developing device. It is an object of the present invention to provide an image forming apparatus capable of performing accurate and stable toner density control. [0010] In order to achieve the above object, according to the first aspect of the present invention, an electrostatic latent image on an image carrier is formed by two images.
An image forming apparatus comprising: a developing device for developing with a component developer; a toner replenishing device for replenishing toner to the developing device; and a magnetic sensor for detecting a toner concentration of the developer in the developing device. Means for causing the developing device to perform the toner replenishing operation intermittently from the end thereof, and the means calculates the output value of the magnetic sensor.
Only when the supplied toner supply time is longer than the specified time,
Causing the toner supply operation of the toner supply device to be performed intermittently,
Otherwise, the toner supply operation of the toner supply device
Are performed continuously . DETAILED DESCRIPTION OF THE INVENTION A dry two-component developer used in a developing device of an image forming apparatus such as a copying machine, a facsimile, a printer, etc. is composed of a magnetic carrier and a non-magnetic toner. In many cases, the change in the toner density, that is, the change in the mixture ratio of the carrier and the toner, directly appears as a change in the magnetic permeability of the developer. A magnetic sensor used to detect the toner concentration of a developer detects a change in magnetic permeability of the developer as a change in voltage, and is usually
It shows output characteristics as shown in FIG. Although it is very important to accurately detect the toner concentration of the developer in order to obtain a good image, the above-mentioned magnetic sensor has a smaller size than the volume of the developing container in which the developing agent is stored in the developing device. Since the toner density detection range is small,
It merely detects the toner concentration of the developer in a limited range around the magnetic sensor. Therefore, in order to accurately determine the toner concentration of the entire developer in the developing device with a magnetic sensor,
The toner must be uniformly distributed throughout the developer in the developing device. Conversely, in order to obtain a good image, the toner in the developer must be uniformly distributed, and when a magnetic sensor is used for toner concentration detection, such a toner uniform distribution state is obtained. For the first time, the accurate toner concentration of the entire developer in the developing device can be known. However, the toner replenishment performed by the toner replenishing device when the toner concentration is reduced is always performed on a part of the developer in the developing device in a state where the toner is more or less densely packed. In order to uniformly distribute the toner throughout the developer, it is necessary to stir the developer with a stirring roller or the like in the developing device. Therefore, the toner density detected by the magnetic sensor can be regarded as an accurate value after the replenishment toner is sufficiently stirred, and a time delay occurs. FIG. 3 shows the change in toner concentration when the toner is replenished in a dense state within the toner concentration detection range of the magnetic sensor and the toner is stirred, as seen from the magnetic sensor. Immediately after the toner is replenished, the toner in the developing device is dense around the magnetic sensor, so that the developer has the same high density within the toner concentration detection range of the magnetic sensor, The output of the magnetic sensor drops from Va to Vc.
Then, as the developer is agitated, the toner is dispersed, and the toner concentration in the toner concentration detection range of the magnetic sensor decreases, so that the output of the magnetic sensor increases from Vc. Thereafter, when the toner is evenly distributed over the entire developer, the output of the magnetic sensor is stabilized at Vb and accurately indicates the toner concentration of the developer in the developing device. The main purpose of the developer stirring action in the developing device is to uniformly disperse the toner in order to obtain a good image and to promote the triboelectric charging of the toner. This also affects the toner concentration detection by the magnetic sensor, and in any case, the ability to disperse the toner more quickly is desired for stirring the developer. Therefore, various stirring devices have been conventionally proposed to increase the stirring ability of the developer. However, as the toner is replenished in a dense state by the toner replenishing device, it takes time to disperse the toner. . The first embodiment of the present invention is an embodiment of the first aspect of the present invention, in which the toner supply operation is continuously turned on during a predetermined toner supply time. In the embodiment, in order to alleviate the toner density caused by the toner replenishing operation, the toner replenishing operation is finely divided into several ON / OFF operations and performed intermittently, so that a small amount of toner can be distributed to many parties. It is intended to be replenished in a dispersed manner. FIG. 4 shows a developing device according to the first embodiment. The first embodiment is an image forming apparatus having a developing device for developing an electrostatic latent image with a dry two-component developer,
For example, an image carrier made of a drum-shaped photoreceptor is rotated by a driving device and uniformly charged by a charging unit, and then an electrostatic latent image is formed by image exposure by an exposure unit. Is transferred by a transfer unit to a transfer material made of transfer paper fed from a sheet feeding device and fixed by a fixing unit, and the photoconductor is cleaned by a cleaning unit after image transfer. In the developing device, as shown in FIG. 4, a dry two-component developer composed of a magnetic carrier and a non-magnetic toner is mixed with each other by stirring members 11 and 12 composed of two stirring screws. The developer is circulated in a developing container 13 composed of a developing hopper by being conveyed in a reverse direction, and the stirring screws 11 and 12 are rotated by a driving device (not shown) to convey the developer in a direction indicated by an arrow in the figure. I do. New toner is supplied to the toner supply unit 14 by a toner supply device (not shown). The toner replenishing device has a toner container such as a toner hopper or a toner cartridge that is detachably mounted, and replenishes the toner in the toner container to the toner replenishing unit 14. The partition plate 15 separates the developers conveyed in opposite directions by the stirring screws 11 and 12, and these developers are transferred by notches provided at both ends of the partition plate 15, and are transferred to the developing hopper. 13 circulates.
The magnetic sensor 16 detects the toner concentration of the developer conveyed by the stirring screw 12. Stirring screw 12
Extends from the developing hopper 13 to the toner replenishing unit 14, and not only transports the developer by rotation, but also takes in the toner replenished to the toner replenishing unit 14 by the toner replenishing device into the developing hopper 13. The developing roller 17 is driven to rotate by a driving device (not shown). The developer is supplied from the stirring screw 11, and the developer is magnetically attracted by an internal magnet to form a magnetic brush. The magnetic brush on the developing roller 17 is conveyed with the rotation of the developing roller 17 and regulated to a fixed amount by a doctor member (not shown), and is supplied to the photoconductor to develop an electrostatic latent image on the photoconductor. . As shown in FIG. 1, a control unit 1 as a control means constituted by using a CPU (microcomputer)
8 reads the output value of the magnetic sensor 16 provided in the developing device 19 at a predetermined timing, and based on the read value, sets the toner replenishing clutch (of the toner replenishing device 20) so that the toner concentration becomes a target value. CL) 21 is turned on / off. The toner supply device 20 includes a toner supply clutch 21
Is turned on to be connected to the drive source to perform the toner supply operation. The toner replenished from the toner replenishing section 14 is conveyed by the stirring screw 12 and is mixed with the developer while being conveyed while being stirred with the developer in the direction indicated by the arrow. Therefore, the control unit 18 controls the magnetic sensor 1
When the toner replenishment unit 20 is caused to replenish the toner based on the output value of No. 6, the toner replenishment from the toner replenishment unit 14 is finely divided into a plurality of times and the toner replenished last time is not left in the toner replenishment unit 14. As shown in FIG. 8, the toner replenishment clutch 21 is turned on / off intermittently so that the next toner replenishment is performed, thereby shortening the time required for the toner to uniformly mix with the developer in the developing device. It becomes possible. The change in the output value of the magnetic sensor 16 during toner replenishment in the first embodiment is as shown in FIG. The time T0 from the start of toner replenishment to the time when the developer and the replenished toner are completely mixed is shorter than in the conventional case where toner replenishment is continuously performed for a predetermined time. Further, even when the control unit 18 reads the output value of the magnetic sensor 16 immediately after toner supply, the control unit 18
If the toner density is treated as the average value Vt of the output of the magnetic sensor 16 for a certain period, there is a high possibility that an output value reflecting toner supply is obtained. Here, in the first embodiment, the control unit 18
In order to detect the toner end of the toner replenishing device (a state in which the toner is empty or a state close thereto), the toner replenishing clutch 21 is forcibly turned on to perform the toner replenishing operation. Detect the end. Further, the control section 18 turns on the toner supply clutch 21 to return from the toner end, and performs toner supply for a long time. As described above, the first embodiment is characterized by claim 1
A developing device 19 for developing an electrostatic latent image on an image carrier with a two-component developer, a toner replenishing device 20 for replenishing toner to the developing device 19, and a developing device In the image forming apparatus having the magnetic sensor 16 for detecting the toner concentration of the developer in the image forming apparatus 19, the control section 18 is provided as means for intermittently performing the toner replenishing operation of the toner replenishing apparatus 20. Accordingly, even in a method of replenishing toner from the end of the developing device, the toner replenished by the toner replenishing device can be promptly reflected on the toner density detected by the magnetic sensor, and accurate toner density control can be performed. . In the first embodiment, the effect of intermittently performing the toner supply operation increases as the toner supply time for performing the intermittent toner supply operation increases. Therefore, in the second embodiment of the present invention, in the first embodiment, the control unit 18 forcibly removes the toner when forming an image with high toner consumption or for detecting the toner end. When the replenishing operation is performed, the intermittent toner replenishing operation is selectively performed such that the intermittent toner replenishing operation is performed only when the toner replenishing operation is performed for a long time to return from the toner end. That is, as shown in FIG. 9, the controller 18 repeatedly takes in the output value of the magnetic sensor 16 at a predetermined timing, calculates the toner supply time from the output value of the magnetic sensor 16, and calculates the toner supply time. The toner supply clutch 21 is intermittently turned on / off so that the above-described intermittent toner supply operation is performed only when is equal to or longer than the specified time. The controller 18 normally turns on the toner replenishing clutch 21 during the toner replenishing time as usual (when the toner replenishing time is not longer than the specified time). The second embodiment is an embodiment of the second aspect of the present invention, and the control unit 18 controls the toner supply of the toner supply device only when the toner supply device performs the toner supply operation for a certain time or more. Since the operation is performed intermittently, stable toner density detection can be performed for various toner supply amounts. In the first embodiment, the toner supply time varies in various ways depending on the amount of consumed toner. Therefore,
In the third embodiment of the present invention, in the first embodiment, as shown in FIG. 6, the control unit 18 controls the on-time of the intermittent toner supply operation (the toner supply is turned on ON / OFF control of the toner replenishment clutch 21 is performed so as to change the off time (the time for turning off the toner replenishment). That is, the control unit 18 controls the toner supply unit 1
In the case of a large amount of toner replenishing operation which may require a more intermittent toner replenishing operation since there is a possibility that a large amount of toner may be accumulated in the toner replenishing unit 4, a toner replenishing clutch is provided so as to take a long time to send the toner from the toner replenishing unit 14 into the developing container 13. By performing on / off control of the toner supply clutch 21, it is possible to reduce the time for mixing the developer and the supply toner, and to turn on the toner supply clutch 21 so that the toner supply operation is completed in a shorter time when a small amount of toner supply is performed. / Off control to enable flexible toner density control corresponding to the situation. The third embodiment is an embodiment of the invention described in claim 1, and the same effects as those of the first embodiment and the above-described effects can be obtained. In the first embodiment, the toner density detection is also performed at the same time as the toner replenishment operation such as a return operation from the toner end, and the toner density control is changed according to the detected toner density value (for example, In the case where the toner replenishing device 20 is used, it may be impossible to wait until the toner supplied from the toner replenishing device 20 is completely mixed with the developer. In such a case, since it takes time to mix the replenished toner and the developer, the control unit 18
Can only estimate the toner density of the entire developer by the toner density value detected by the magnetic sensor 16. However, the toner supplied from the toner replenishing device 20 is conveyed in the developing device and passes over the magnetic sensor 16. The interval at which the toner is supplied depends on the interval at which the intermittent toner supply operation is turned on (the interval at which toner is supplied) and the toner transport speed in the developing device. Therefore, the fourth embodiment of the present invention differs from the first embodiment in that the toner concentration is detected at the same time as the toner replenishment operation such as a return operation from the toner end, and the detected toner is detected. Change the toner density control according to the density value (for example, release the toner end)
The interval for taking in the output value of the magnetic sensor 16 in the toner concentration detection is set to a time that always includes the toner concentration change due to the toner supplied from the toner supply device 20, as shown in FIG. The interval at which the toner density is detected by the magnetic sensor 16 and the interval at which the intermittent toner supply operation by the toner supply device 20 is turned on (interval of the intermittent operation of toner supply) are set differently. As a result, it is possible to obtain a toner density detection value that is not different from the actual toner density even immediately after toner supply by the intermittent toner supply operation. As described above, according to the present invention , a developing device for developing an electrostatic latent image on an image carrier with a two-component developer, and toner is supplied to the developing device. In an image forming apparatus having a toner replenishing device and a magnetic sensor for detecting a toner concentration of a developer in the developing device, a toner replenishing operation of the toner replenishing device is performed with respect to the developing device from an end thereof. > comprising means for intermittently performed, said means, said magnetic sensor
The toner supply time calculated from the output value of the
Only in the above case, the toner supply operation of the toner supply device is performed.
The toner replenishing device otherwise.
, The toner replenishing operation is continuously performed. Therefore, even in a system in which the toner is replenished from the end of the developing device by the toner replenishing device, the toner replenished by the toner replenishing device is promptly reflected on the toner concentration detected by the magnetic sensor. until
Time (until it becomes uniformly mixed with the developer)
And hinders accurate toner concentration control.
Was eliminated, and the toner was
The time required for uniformity can be reduced. [0038]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a control system according to a first embodiment of the present invention. FIG. 2 is a characteristic diagram showing output characteristics of a magnetic sensor. FIG. 3 is a waveform diagram showing output values of a magnetic sensor when toner is replenished in a toner density detection range in a dense state and stirred. FIG. 4 is a cross-sectional view illustrating a developing device according to the first embodiment. FIG. 5 is a waveform diagram showing a change in an output value of a magnetic sensor when toner is supplied in the first embodiment. FIG. 6 is a timing chart showing the operation timing of the third embodiment of the present invention. FIG. 7 is a timing chart showing the operation timing of the fourth embodiment of the present invention. FIG. 8 is a flowchart showing an operation flow of the first embodiment. FIG. 9 is a flowchart showing an operation flow of the second embodiment of the present invention. [Description of Signs] 11, 12 Stirring screw 13 Developing container 14 Toner replenishing unit 15 Partition plate 16 Magnetic sensor 17 Developing roller 18 Control unit 19 Developing device 20 Toner replenishing device 21 Toner replenishing clutch

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/08

Claims (1)

(57) Claims: (1) A developing device for developing an electrostatic latent image on an image carrier with a two-component developer, a toner replenishing device for replenishing toner to the developing device, and the developing device in the image forming apparatus and a magnetic sensor for detecting the toner density of the developer in the apparatus, comprising means for intermittently performed from the end portion of the toner supply operation of the toner supply device to said developing device, said The means includes a toner calculated from an output value of the magnetic sensor.
-Toner replenishment only when replenishment time is longer than specified time
Make the machine replenish the toner intermittently.
In this case, the toner supply operation of the toner supply device is continuously performed.
Image type forming apparatus characterized by causing I.